A cold-rolled and heat-treated steel sheet having a microstructure of, in surface fraction: between 10% and 30% of retained austenite, said retained austenite being present as films having an aspect ratio of at least 3 and as Martensite Austenite islands, less than 8% of such Martensite Austenite islands having a size above 0.5 m, at most 10% of fresh martensite and recovered martensite containing precipitates of at least one element chosen among niobium, titanium and vanadium. A manufacturing method thereof is also provided.

A steel sheet for hot press comprises: a predetermined chemical composition; and a steel microstructure that includes ferrite and cementite and in which Mn/Mn is 1.4 or more, where Mn is a Mn concentration of the ferrite and Mn is a Mn concentration of the cementite.

A steel part includes a steel sheet substrate and a coating on at least one surface of the steel sheet substrate. The coating includes between 0.2 and 0.7% by weight of Al, with a remainder of the metal coating being Zn and inevitable impurities. The steel sheet substrate and the coating have at least one deformation. An outer surface of the coating has a waviness Wa.sub.0.8 of less than or equal to 0.43 m.

A kind of steel is able to achieve a high elongation with the steel used for hot stamping by means of simple hot stamping process. The formed component has excellent yield strength, tensile strength and elongation. The steel used for hot stamping comprises by weight percent 0.1-0.19% of C, 5.09-9.5% of Mn, 0.11-0.4% of V, and 0-2% Si+Al, wherein the combination of C and V meets one of the following two requirements: 1) 0.1-0.17% of C and 0.11-0.4% of V; and 2) 0.171-0.19% of C and 0.209-0.4% of V.

The present invention provides a method for manufacturing a metal sheet. In this method, at least one of the following equations is satisfied: $\begin{array}{cc}\frac{Z}{d}+18\ln \left(\frac{Z}{d}\right)<8\ln \left(\frac{P}{V}\right)-27.52& \left(A\right)\\ f{O}_2<\frac{2.304.Math.{10}^{-3}}{{(27.52+\frac{Z}{d}+8\ln (}^{}}\end{array}$

A process for producing a steel component with a metallic, corrosion protection coating and very good mechanical properties may involve directly applying an iron-based alloy to a steel substrate. The iron-based alloy may contain 50-80% by weight of Fe, 0-30% by weight of Mg, 0-5% by weight of Al, 0-5% by weight of Ti, 0-10% by weight of Si, 0-10% by weight of Li, 0-10% by weight of Ca, 0-30% by weight of Mn, and a balance of Zn and unavoidable impurities. The steel substrate that has been coated with the iron-based alloy may then be subjected to hot forming in order to obtain the steel component. A metallic coating that protects against corrosion for steel components to be produced by the process of hot forming can be obtained.

The present invention provides a cold-rolled and annealed steel sheet of thickness between 0.7 mm and 2 mm, mechanical strength ranging from 1180 MPa to 1320 MPa, wherein the hole expansion ratio Ac % is greater than 20% and the bending angle is greater than or equal to 40. The chemical composition includes, the contents being expressed as weight percent: 0.09%C0.11%, 2.6%Mn2.8%, 0.20%Si0.55%, 0.25%Cr<0.5%, 0.025%Ti0.040%, 0.0015%B0.0025%, 0.005%Al0.18%, 0.08%Mo0.15%, 0.020%Nb0.040%, 0.002%N0.007%, 0.0005%S0.005%, 0.001%P0.020%, Ca0.003%, the remainder being iron and inevitable impurities resulting from processing. The sheet has a microstructure including martensite or lower bainite. A sum of the surface fractions of martensite and lower is between 40% and 70%, from 15% to 45% of the surface fraction is low-carbide bainite, from 5% to less than 20% of the surface fraction is ferrite, the non-recrystallized ferrite fraction relative to the total ferrite fraction is less than 15%, and less than 5% of the surface fraction of residual austenite is in the form of islands. The fraction of former austenitic grains in which the size is less than at least one micrometer represents 40% to 60% of the total population of the former austenitic grains.

The present invention provides a method for manufacturing more beautiful black coated steel sheets by uniformly blackening the coating layer. Specifically, the present invention provides a method for manufacturing black coated steel sheets, which brings ZnAlMg alloy coated steel sheets (1) into contact with steam in a closed container (10), wherein said closed container (10) can maintain a predefined internal pressure through variable control of the amount of steam flowing into said closed container (10) and/or the amount of steam flowing out of said closed container (10), and in said closed container (10) that can maintain said predefined pressure, said ZnAlMg alloy coated steel sheets (1) have contact with the steam introduced into said closed container (10).

A method for operating a continuous processing line including an annealing step for the production of continuously processed rolled steel strip using a computer aided dynamic property predictive control model.

A chassis component for a motor vehicle is disclosed. The chassis component (1) is manufactured at least partially from a multi-layer steel sheet (10, 20, 30). The multi-layer steel sheet (10, 20, 30) includes at least three steel layers, including two outer steel layers (11, 12; 21, 22; 31, 32) and one inner steel layer (13, 23, 33). At least one outer steel layer (11, 12; 21, 22; 31, 32) of the multi-layer steel sheet (10, 20, 30) has a tensile strength of at least 1200 MPa. A method for producing a chassis component for a motor vehicle, in particular a wheel (1) or a part thereof, is also disclosed.